Cosmetic products (e.g., foundation products) are typically applied to the entire face to mask perceived imperfections in skin texture (i.e., fine lines and wrinkles), pigmentation or vascularization. It is desirable for foundations to mask these imperfections and yet still allow for a natural appearance of the skin. In other words, consumers want good coverage from a foundation product, but do not want the appearance of too much make-up, i.e., cakey appearance.
Pigmented oil-in-water and water-in-oil emulsion cosmetic products are a popular type of cosmetic product available on the market today. These products are relatively inexpensive and are easy to apply to the skin. Moreover, the pigmented oil-in-water or water-in-oil emulsion foundation lends itself to variation in pigment type and level to give different degrees of color coverage.
However, it is believed that, in order to minimize the appearance of fine lines and wrinkles and to avoid a cakey appearance when utilizing a certain cosmetic products, it is important to deposit the pigment particle or solid particle from the cosmetic product uniformly of the skin. Unfortunately, the tendency of the solid particles is to agglomerate (i.e., flocculate) in the foundation product and, upon application of the foundation product to the skin, to collect in the fine lines and wrinkles or otherwise agglomerate on the skin, thereby accentuating, rather than minimizing the appearance of the fine lines, and further providing a cakey, unnatural appearance to the skin.
Preventing agglomeration (flocculation) of the solid particles in foundation products and upon application to the skin can be very difficult. One way to improve the stability of solid particles in foundation products is to “coat” the particle; in other words, adsorb certain materials onto the surface of the particle. See Driscoll, P., “Treated Pigments in Decorative Cosmetics”, Cosmetics and toiletries, Vol. 104 (July 1989), pp 43-45. Foundation and other personal care products containing hydrophobically or hydrophilically coated pigments are know in the art (See, for example, Lee, J et al., Preparation of Ultra Fine Fe3O4 Particles by Precipitation in the Presence of PVA at High pH”, J. Colloid Interface Sci., 177, p. 490 [1996] and European Patent Application 504,066, published Mar. 13, 1992). Unfortunately, the methods taught in the art for preventing agglomeration of pigment particles in product and when applied to skin are not sufficient to provide products which meet consumer needs with respect to the natural appearance of the skin.
Another problem associated with the use of solid particles relates to the size of the particle. Solid particles having a particle size greater than 20 microns are difficult to disperse within the droplet phase of emulsions typically regarded as stable emulsions since such emulsions typically have discontinuous phase droplets of droplet size less than 20 microns. The smaller droplets avoid the “buoyancy effect” (i.e., where the buoyancy force of the discontinuous phase droplet exceeds the viscous forces of the continuous phase) associated with droplets having droplet sizes greater than 20 microns. Additionally, the surfactants or emulsifiers typically used in such emulsions do not tend to provide the structurant properties necessary to support emulsions having larger sized droplets (i.e., greater than 20 microns).
It has now been found, however, that cosmetic products can be formulated wherein the agglomeration of solid particles contained therein is minimized and wherein the skin deposition control is improved using the technology hereinafter described. Specifically, it has been found that the use of emulsifying type elastomers aid in controlling agglomeration of solid particles dispersed within the discontinuous droplet phase and provide stable emulsions supporting discontinuous phase droplets having a particle size greater than 20 microns. Moreover, when the cosmetic products of the present invention are applied to the skin, solid particles having a broad particle size distribution are capable of being uniformly deposited on the skin. Without being limited by theory, these solid particles are delivered to the skin by means of emulsion droplets having a broad droplet size distribution. Specifically, the solid particles, even those having a particle size greater than 20 microns, are dispersed within and/or at the droplet interface of the emulsion system such that capillary-induced agglomeration of the particles is confined within the space or volume occupied by the droplet, thereby providing a more even distribution of the broad range particles on skin. Additionally, the droplets serve as a barrier preventing agglomeration as a result of application shear. Accordingly, good coverage of the skin and a natural appearance of the skin is provided.
Accordingly, one aspect of the present invention is to provide cosmetic compositions which control agglomeration or flocculation of pigments in the cosmetic product and when applied to skin.
Another aspect of the present invention is to provide improved distribution of pigments on skin.
Still another aspect of the present invention is to provide good coverage of the skin as well as retain the natural appearance of the skin.
These and other aspects of the present invention will become more readily apparent from consideration of the following summary and detailed description.